1. Field of the Invention
The present invention generally relates to methods for allocating cost and more particularly to a causal methodology for costing product processing.
2. Description of the Related Art
The spiraling cost of semiconductor production has driven the industry to pursue greater economies of scale. This trend has forced a move from smaller, single partnumber fabricators to bigger, multiple partnumber, multiple technology fabricators. Costing is easy in a single partnumber fabricator and involves simply dividing total spending by the total units produced. Difficulties arise in costing wafer processing not as a result of complex processing or advanced tooling requirements, but rather as a result of diverse and extensive product offerings. Multiple partnumber, multiple technology fabricators must develop methodologies for costing different products. Traditional accounting systems track cost by department, not by partnumber, so developing a methodology which accurately assigns cost by partnumber becomes a key concern. Conventional cost-of-ownership models provide detailed cost data of equipment assets but not wafer processing costs. What is needed is a cost model that goes beyond classical cost-of-ownership data to provide accurate processing costs for such items as semiconductor wafers.